Clunking noise from rear end at track event...

[Cannon]

Ok, at the last OT event I was at, my trusty steed let me down. I was halfway through the last day at Buttonwillow when I began hearing (and feeling) a very pronounced clunk from the rear end. It only happened when the suspension was loaded laterally, and began w/ the right side, followed shortly by the left side. It was most definitely tire speed dependent and the sound seemed to be coming from the inside tire in corners. Very strange.

The car had my track tires and pads on it at the time (stock rims w/Yoko A-032R's and Carboteck Panther Plus pads). I decided to call it a day since I still had to drive the car home. I pulled into the pits and immediately checked everything I could think of. Checked all four tires for any kind of play in the bearings. Nope. Pulled all four tires off, and looked around. Nothing obviously wrong. Hmmmmm.

I drove home, swapped back to stock tires/brakes, and attempted to duplicate the problem. Couldn't duplicate it. I tried everything. Violent left right transitions, steady state cornering, canyon blasts, and the car behaved perfectly with no unusual noises or vibrations. WTF?

Well, I've got another open track event this weekend at Buttonwillow, and am a bit concerned that this problem will manifest itself again and ruin my weekend.

Any Ideas as to what it could have been?

Chris

[Pierre]

It's probably your rear shock mounts. They go bad frequently.
East to fix.

[CiaoBoy]

otherwise the clunking would have still been there despite switching back to your original tires and brakes.

-CiaoBoy

[Pierre]

Well, at least it's worth a try to check those rear shock mounts. Another possibility is your lower control arm bushings. Jack up the rear of the car and yank on the rear lower control arm (boomerang shaped, large) If there is any play, you have a worn out bushing.

[CiaoBoy]

Originally posted by Pierre
Well, at least it's worth a try to check those rear shock mounts. Another possibility is your lower control arm bushings. Jack up the rear of the car and yank on the rear lower control arm (boomerang shaped, large) If there is any play, you have a worn out bushing.

Worn bushings wouldn't make a clunking noise, would they? I thought worn bushings would result in less precise handling, but that's about it.

-CiaoBoy

[Pierre]

Well, I changed mine to solid TC Kline race bushings before they went bad, so I do not have personal experience with the noise they make. I'm just trying to give you suggestions on things to check.

[CiaoBoy]

Originally posted by Pierre
Well, I changed mine to solid TC Kline race bushings before they went bad, so I do not have personal experience with the noise they make. I'm just trying to give you suggestions on things to check.

Actually, looking back at his original post, it sounds like the problem should be related to the tires/wheels. Once he put the stock tires/wheels back on, the symptom disappeared. It's probably not the brakes, since it's doubtful they would make such a noise.

-CiaoBoy

[Cannon]

Thanks for the responses. I just remembered that when I was pulling the left rear caliper off, the caliper made a loud *pop* as soon as I pulled out the first guide pin. Almost like it was pre-loaded or stressed somehow.

I've swapped pads about 7 times on this car, so I'm pretty sure they were installed correctly on the track, so I'm not sure how the caliper could have gotten in such a postition that it would pop loose like that when removed. I looked at both guide pins very closely, and they seem to be fine.

:

Chris